This invention relates to a method and apparatus for reducing interference in a wireless device. While the invention is particularly directed to the art of telecommunications and will be thus described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications.
By way of background, people frequently use communication networks on a daily basis at work, at home, and on the road. Consequently, many people carry a wireless device, such as a cell phone, a PDA, a BlackBerry, etc, when they are in transit. At home, people have access to a landline phone and/or a PC connected to a public network. With this access to communication devices, people are able to contact emergency services, such as 911 services, in case of an emergency event (e.g., a fire, a medical emergency, a burglary, etc).
“911” has been designated in the United States as the number to be used by the public to summon emergency aid or to report a crime, fire, or accident. A caller in response to an emergency event dials 9-1-1 on their telephone. In the original 911 service, known as Basic 911 (B911), the call is routed to one centralized answering location. The agent at the answering location converses with the caller to obtain pertinent information on the emergency event. The agent then determines the appropriate agency or emergency personnel to dispatch, and dials the number to transfer the caller to that agency. Enhanced 911 services, or E911, provide some enhancements to the Basic 911 service. For instance, E911 automatically provides the agent with information on the caller, such as a street address, medical conditions, etc. That way if the caller is incapacitated in some manner, then the emergency personnel would be able to go to the location of the caller.
A wireless communications device such as a mobile phone may be equipped with a GPS (Global Positioning System) receiver to support geo-location services. However, E911 service may cause interference with the built-in GPS receiver due to the second harmonic of its mobile transmission when the mobile phone transmit frequency range falls within half of the GPS frequency band.
For example, the GPS L1 Band (Civilian Navigation) has a range from 1565.42 MHz to 1585.42 MHz, and it is centered at 1575.42 MHz. The second harmonic of the Upper 700 MHz C or D Block mobile transmitter could interfere with its own L1 Band GPS receiver.
This problem can be addressed through mobile RF circuitry design, such as implementing better antenna isolation or using a better low-pass filter, etc. However, such solutions may be very costly and prove more difficult to implement. For example, a good low-pass filter may cost more than the mobile device itself. And any antenna isolation circuitry may be complicated in design, especially in a small space like mobile device.
The present invention contemplates a new and improved that resolves the above-referenced difficulties and others.